Polyvinylpyridinium anion-exchangers for recovery of technetium and plutonium anions

ABSTRACT

Described are anion-exchange materials having extraordinarily high affinity for plutonium anions such as plutonium (IV), and technetium anions such as pertechnetate. Preferred inventive resins are highly divinylbenzene cross-linked polyvinylpyridine resins exhibiting a macroreticular bead form, which have been quaternized to contain a substantial amount of 1-alkyl-pyridinium groups wherein the alkyl group has 4 to 8 carbon atoms. The inventive resins can be used in preferred processes for recovering plutonium and/or technetium anions from aqueous mediums, for example nuclear waste streams or groundwater related to civilian or defense-related nuclear operations.

BACKGROUND

The present invention relates generally to anion-exchangers forrecovering metal values from aqueous solutions, and in particular tocrosslinked polyvinylpyridinium anion-exchange resins and their use inrecovering anions of radioactive elements such as technetium andplutonium.

As further background, as a consequence of the development andutilization of nuclear fission technologies, large amounts of civilian-and defense-related radioactive nuclear wastes have been and continue tobe produced. While some nuclear wastes are handled simply in controlledgeological repositories, other waste streams are reprocessed to removeor recover radioactive isotopes. For example, technetium⁹⁹ (Tc⁹⁹) is aradioactive material which is a fission product of uranium or plutoniumused for nuclear fuel. In most aqueous environments, Tc⁹⁹ forms a stableanion, known as pertechnetate (TcO₄ ⁻). Pertechnetate is soluble inbasic, neutral and acidic aqueous mediums and thus very mobile in avariety of environments. Accordingly, it is critically important innuclear waste reprocessing strategies, and- in nuclear site remediation,to deal with the mobile pertechnetate ion.

Plutonium also forms stable ions which are desirably recovered in thereprocessing of nuclear waste streams or in the recovery of plutoniumfrom impure scrap materials from plutonium facilities. To date, the twoclassical methods for recovering technetium and plutonium values havebeen liquid-liquid extraction and liquid-solid ion-exchange processes.In the field of ion-exchange, one common practice has been to purifyplutonium by anionic exchange in nitric acid. As for technetium, thepertechnetate ion exists in acidic, neutral and basic mediums, and thusits associated ion-exchange purifications occur from a wide range offeed materials.

While these ion-exchange processes have generally proven to be operable,ion-exchange resins having greater affinity for ions of plutonium andtechnetium are needed. The present invention addresses this need.

SUMMARY OF THE INVENTION

The applicant has prepared anion-exchange materials which exhibitextraordinarily high affinity for anions of plutonium and technetium,enabling improved processes for separating these anions from solutionssuch as those generated during nuclear waste processing. In accordancewith the present invention, these anion-exchange materials comprisecopolymers of divinylbenzene and vinylpyridine, which contain at least15% by weight divinylbenzene (w/w relative to vinylpyridine) to providean effective crosslink density and advantageous physical properties, andwhich have had a substantial amount of their pyridyl groups converted to1-(C₄ -C₈ alkyl)-pyridinium. It has been discovered that the use ofrelatively longer 1-alkyl groups such as butyl, pentyl, hexyl, heptyland octyl, provides pyridinium resins with unexpectedly improvedaffinity for anions of plutonium and technetium as compared topyridinium resins bearing 1-methyl groups. Thus, provided by the presentinvention are preferred, highly crosslinked bead-form anion exchangeresins having substantial pendant 1-alkyl-pyridinium groups, wherein the1-alkyl groups are branched or unbranched and have 4 to about 8 carbonatoms. Especially preferred resins of the invention are provided whereinthe 1-alkyl groups have from 4 to 6 carbon atoms.

These anion exchange materials can be prepared by a preferred processwhich involves post-functionalizing a bead-form copolymer ofdivinylbenzene and vinylpyridine. For example, thepost-functionalization can include a process in which a reaction mediumis formed containing the copolymer slurried in an organic solvent alongwith an alkylating agent, R-L, wherein R is a branched or unbranchedalkyl group having 4 to 8 carbon atoms and L is a leaving group ofsufficient strength to lead to the quaternization of pyridine nitrogensby the alkylating agent. For example, L is preferably a halide or analkyl or aryl sulfonate group. The reaction medium is heated to atemperature and for a period of time sufficient to substantiallyalkylate, or quaternize, the pendant pyridinyl groups of the polymer. Inthis regard as used here and throughout this document, "substantiallyquaternized" is intended to mean that at least about 20 mole percent ofthe pyridinyl groups of the polymer material (based on the amount ofvinylpyridine included in the resin) are quaternized.

The strong-base anion-exchange resins of the invention are useful in abroad range of anion-exchange processes for recovering technetium and/orplutonium values. For example, they can be used in the recovery oftechnetium values as pertechnetate from nuclear waste tank materials orin groundwater treatment operations. In addition, the anion-exchangersof the invention can be used in the purification of Pu as Pu(IV) innitric acid anion-exchange processes. In these methods, the inventivematerials provide high affinity and good sorption kinetics fortechnetium and plutonium anions, for rapid and efficient loading of theresin. These and other embodiments, objects and advantages of thepresent invention will be readily apparent from the followingdescription.

DESCRIPTION OF THE PREFERRED EMBODIMENT

For the purpose of promoting an understanding of the principles of theinvention, reference will now be made to certain preferred embodimentsthereof and specific language will be used to describe the same. It willnevertheless be understood that no limitation of the scope of theinvention is thereby intended, such alterations, further modificationsand applications of the principles of the invention as described hereinbeing contemplated as would normally occur to one skilled in the art towhich the invention relates.

As indicated above, the present invention provides strong baseanion-exchange resins having extraordinarily high affinity for plutoniumand technetium anions. The preferred anion-exchange resins comprisehighly (15%+) crosslinked bead-form copolymers which contain substantialpendant 1-(C₄ -C₈ alkyl)-pyridinium groups. The preferred resins willthus bear substantial repeating units of the formula (I): ##STR1##

wherein R is a branched or unbranched C₄ to C₈ alkyl group, and X⁻ is ananion. In this regard, preferred resins of the invention will be atleast about 20% by weight comprised of repeating units of formula (I),typically in the range of about 20% to about 80% by weight, in order toprovide an effective number of anion-exchange sites for advantageousseparation of technetium and/or plutonium anions from aqueous solutions.

Representative groups R thus include branched or unbranched butyl,pentyl, hexyl, heptyl or octyl groups. Representative groups X⁻ includeions typically resulting from the alkylating agent, for instance halides(including chloride, bromide, iodide and fluoride) or alkyl or arylsulfonate groups of the formula R¹ SO₃ ⁻ wherein R¹ is an alkyl or arylgroup, typically having from 1 to 20 carbon atoms. Groups X⁻ may alsorepresent counterions of strong acids which have been used to displacethe original anion of the formed quaternary pyridinyl group, for examplenitrate or sulfate ions. It will be understood that the anion X- may bevaried widely to facilitate the use of the inventive resins in specificsituations. For example, when the resin is to be used in an anionexchange process in nitric acid for the recovery of plutonium, it willbe preferred to pretreat the resin with nitric acid to put it in thenitrate form. These and other modifications of the anion X⁻ will readilyoccur to those skilled in the pertinent chemical field.

In especially preferred resins of the invention, the quaternizing alkylgroup R will have 4 to 6 carbon atoms. The resultant resins exhibit highaffinity and advantageous sorption kinetics for plutonium and technetiumanions, and also good wetability with aqueous solutions, a highlyimportant factor in the conduct of the target aqueous anion-exchangeprocesses.

It will be understood that in preferred resins wherein not all of thepyridinyl groups present are quaternized to form 1-alkyl-pyridiniumgroups, the resins will also include repeating units of the formula(II): ##STR2##

and/or acid salt forms of the repeating unit of formula (II), forexample which would occur upon treating the resins with a strong acidsuch as nitric acid or sulfuric acid, as discussed above.

In the preferred inventive resins the mole ratio of repeating units (I)to repeating units (II) will be at least about 1:4 and typically will bein the range of about 1:4 to about 19:1. Stated another way, typically,about 20 mole % to about 95 mole % of the pyridinyl repeating units inthe resin will be quaternized.

As to the preparation of inventive resins, this preferably begins withthe preparation of a highly divinylbenzene-crosslinked, free base formpolyvinylpyridine polymer, for example using procedures as generallydescribed in U.S. Pat. No. 4,221,871. Poly 2- or 4-vinylpyridinepolymers are preferred, although alkyl-substituted vinylpyridinepolymers, for example poly-2-methyl-5vinylpyridine polymers, are alsosuitable. The vinylpyridine monomer used to prepare resins of theinvention is preferably of relatively high purity, for example at leastabout 90% pure. The charge of vinylpyridine to the copolymerization willbe substantial, in order to provide substantial pendant pyridine groupsand an effective level of functionality to the copolymer. Preferably,the copolymer is at least about 50% by weight comprised ofvinylpyridine, often falling in the range of 50% to 85% by weightvinylpyridine.

The preferred divinylbenzene crosslinker used in the invention is alsodesirably of high purity, for example about 80% or more pure. The chargeof divinylbenzene to the copolymerization will typically be in the rangeof 15% to 50% weight to weight (w/w) relative to the vinylpyridinecharged. Particularly advantageous copolymers result from the use ofabout 20% to about 30% divinylbenzene, most preferably about 25% (w/wrelative to vinylpyridine).

Preferred resins of the invention are bead-form gel or macroreticularresins, with a mesh size in the range of about 20 to 80 mesh, morepreferably about 30 to about 60 mesh. Bead form macroreticular resinsare most preferred.

Suitable copolymer resin starting materials for use in the inventioninclude products known as REILLEX™ 425 and REILLEX™ HP resins,commercially available from Reilly Industries, Inc. of Indianapolis,Ind., U.S.A. These materials are 25% divinylbenzene-crosslinkedpoly-4-vinylpyridine resins exhibiting a macroreticular bead form. TheseREILLEX™ resins are highly thermally stable, for example at least up totemperatures of about 200° C. As well, these REILLEX™ resins demonstratesubstantial stability against chemical or mechanical breakdown whensubjected to ionizing radiation such as that typical of Tc⁹⁹ or Pu²³⁹recovery or clean-up operations.

In addition to vinylpyridine and divinylbenzene, copolymers of theinvention may also include minor amounts of other comonomers such asstyrene, but typically in amounts less than about 10% w/w relative tovinylpyridine.

The alkylating agent used in the invention will generally be of theformula R-L wherein L is a leaving group effective to confer upon thealkylating agent the ability to alkylate pyridine nitrogens. L willusually be a halogen or an alkyl or aryl sulfonate group as discussedabove. With regard to halogens, those other than iodine, especiallychlorine and bromine, are preferred. It has been found that iodideresultant of quaternizations with alkyl iodides is difficult to removefrom the formed anion-exchange resins, for example when converting theresins to another form such as the nitrate form.

In the quaternization process, the alkylating agent is contacted withthe resin in organic solvent system, e.g. a polar organic solvent suchas dimethyl sulfoxide (DMSO) or an alcohol, especially lower (C₁ -C₄)alcohols such as methanol and ethanol. It will be understood that thesolvent should be compatible with the resin and the alkylating agent,and should be readily removable (e.g. rinsable or dryable) from theresin after completion of the reaction. The quaternization reactions canbe performed at atmospheric or superatmospheric pressures. When it isdesired to obtain a high level of quaternization, the reaction willtypically be conducted at superatmospheric pressures. For example, thereaction medium containing the solvent, the resin and the alkylatingagent can be formed in a closed reactor such as an autoclave, and thereaction mixture can then be heated and reacted at the autogenouspressure of the reaction system.

The quaternization reaction will be carried out at a temperature and fora period of time sufficient to quaternize a substantial amount of thepyridinyl groups in the polymer. In preferred processes and resins,about 40 mole % to about 95 mole % of the pyridinyl repeating units willbe quaternized, or converted to the 1-alkyl-pyridinium form. Given theteachings herein, the extent of quaternization will be a parameterreadily controlled by those skilled in the art to optimize theperformance of the inventive resins in a given application.

In some instances, as a further preparative step or in situ in a useenvironment, the initially-prepared product will be treated to replacethe anions resulting from the leaving groups (L⁻) with another anionsuited to or resultant of an end use of the resins. This treatment may,for example, involve contacting the resin with a strong, inorganic acidsuch as nitric acid or sulfuric acid, to introduce nitrate or sulfategroups, respectively. It will be well understood that in suchoperations, some or all of the free base form pyridine groups remainingin the resin will be converted to their protonated, acid salt form.Thus, preferred resins of the invention may contain free base and/oracid salt form pyridinyl groups in addition to the substantialquaternary salt form pyridinyl groups.

As to the use of the inventive resins, the manipulative steps of theanion-exchange processes for the recovery of plutonium and technetiumanions can be performed in a conventional fashion. For example, innitric acid anion exchange for plutonium recovery, the nitric acidsolution containing PU(IV) can be passed through a column containing theinventive anion-exchange resin, to selectively sorb Pu(IV) to the resin.Similarly with regard to technetium, solutions containing pertechnetate,including for example groundwater or neutral, acidified or basifiednuclear waste reprocessing solutions, can be passed through such acolumn to selectively sorb pertechnetate to the inventive resins. Thethus-bound plutonium or technetium can then be eluted from the resinsusing conventional techniques, or, alternatively, the resin can serve asa solid fixation device which is transferred to a geologic repository,or fed to a technetium recovery process in which the resin is destroyed(e.g. incinerated) while recovering the technetium values.

For the purposes of promoting a further understanding of the inventionand its principles, the following specific Examples are provided. Itwill be understood that these Examples are illustrative and not limitingin nature. In these Examples, the chloride exchange capacities weredetermined by saturating a known quantity of resin with a solutioncontaining chloride ion, rinsing the column of excess chloride solution,displacing the chloride ion with excess sulfate ion, collecting theeffluent containing the chloride and determining, using standardmethods, the quantity of chloride ion initially adsorbed the thendisplaced from the resin. The mole % quaternizations of the resins weredetermined by the ratio of the chloride exchange capacity inmilliequivalents per gram (meq/g) dry resin to the pyridine function(meq/g) based on the vinylpyridine portion of the total monomers used toprepare the crosslinked polyvinylpyridine.

EXAMPLE 1 Preparation of 1-n-Butyl Poly-4-Vinylpyridinium Chloride,Crosslinked

150 g of a bead-form, 25% crosslinked poly-4-vinylypyridinemacroreticular resin (REILLEX™ HP resin) were first dried and thenslurried with dimethyl sulfoxide (1L) and allowed to soak overnight.1-Chlorobutane (191 g) was added with heating and stirring during aboutone and one-half hours. Heating and stirring were continued under refluxconditions for about 120 hours at between 85° to 110° C. The slurry wascooled and filtered and the product washed with several portions ofmethanol and dried. The product was 43% quaternized and exhibited achloride exchange capacity of 2.22 meq/g dry resin.

EXAMPLE 2 Preparation of 1-n-Hexyl Poly-4-Vinylpyridinium Chloride,Crosslinked

150 g of REILLEX™ HP resin were dried and slurried with dimethylsulfoxide (1L) as in Example 1. 1-Chlorohexane (248 g) was added withheating and stirring during about 2 hours. Heating and stirring werecontinued under reflux conditions for about 94 hours at 100°-110° C. Theslurry was cooled, filtered, and the product washed with severalportions of methanol and dried. The product was 45% quaternized,exhibiting a chloride exchange capacity of 2.15 meq/g dry resin.

EXAMPLE 3 Preparation of 1-n-Octyl Poly-4-Vinylpyridinium Chloride,Crosslinked

150g of REILLEX™ HP resin were dried and slurried in dimethyl sulfoxide(1L) as in Example 1. The slurry was heated with stirring. The additionof 1-chlorooctane (307 g) was begun when the slurry's temperature hadreached 80° C. and completed two and one-half hours later when theslurry's temperature had reached 95° C. The slurry's temperature wasincreased and maintained at 95°-110° C. under reflux condition withcontinued stirring for about 94 hours. The slurry was cooled andfiltered and the product washed with several portions of methanol anddried. The product exhibited a chloride exchange capacity of 2.44 meq/gdry resin. 59 mole % of the pyridyl groups of the polymer had beenquaternized.

EXAMPLE 4 Preparation of 1-n-Butyl Poly-4-Vinylpyridinium Chloride,Crosslinked

Water-wet REILLEX™ HP resin (150 g) was slurried with about 200 mL ofmethanol and, after about 30 minutes, the liquid portion was decanted.The procedure was repeated with an additional 200 mL portion ofmethanol. The resulting methanol-wet polymer, 200 mL of fresh methanol,and 137 g of n-butyl chloride were added to a TEFLON®polytetrafluoroethylene-lined autoclave and heated to 115° C. for 87hours under autogenous pressure. The autoclave and its contents werecooled, the autoclave vented and the reaction mixture removed. Theslurry was filtered and rinsed with additional methanol. The resultingproduct was found to be 89% quaternized, and to have a chloride exchangecapacity of 3.75 meq/g dry resin.

EXAMPLE 5 Preparation of 1-Isobutyl Poly-4-Vinylpyridinium Chloride,Crosslinked

Water-wet REILLEX™ HP resin (150 g) was slurried with about 200 mL ofmethanol and, after about 30 minutes, the liquid portion was decanted.The procedure was repeated with an additional 200 mL portion ofmethanol. The resulting methanol-wet polymer, 200 mL of fresh methanol,and 103 g of isobutyl chloride were added to a TEFLON®polytetrafluoroethylene-lined autoclave and heated to 100° C. for 68hours under autogenous pressure. The autoclave and its contents werecooled, the autoclave vented and a small sample of the reaction mixturewas removed for analysis. An additional 34.3 g of isobutyl chloride wereadded to the slurry and the reaction mixture again heated to 100° C. for68 hours. The autoclave and its contents were cooled, the autoclavevented, and the resulting reaction mixture removed. The slurry wasfiltered and rinsed with additional methanol and a portion of thepolymer dried. The resulting sample was found to be about 45%quaternized, exhibiting a chloride exchange capacity of 2.40 meq/g dryresin.

EXAMPLE 6 Analysis of Resins for Affinity for Plutonium Anions

The distribution coefficients (Kd) of Pu(IV) from nitric acid solutionsonto the resins prepared in Examples 1-5 were measured generally aspreviously described by S. F. Marsh, "Improved Recovery and Purificationof Plutonium at Los Alamos Using Macroporous Anion Exchange Resin," LosAlamos National Laboratory Report LA 10906 (May 1987), and compared tothat of REILLEX™ HPQ resin, a commercially available approximately60-70% methyl quat of REILLEX™ HP resin (the material used in this studyassayed at 62% quaternization). Thus, a solution containing Pu(IV) wasprepared having an initial Pu concentration of 3 g/L. Small scaledynamic contacts between resin and plutonium solutions were effected forthe contact periods given in Table 1, on a wrist-action shaker. Measuredportions of the aqueous Pu(IV) solutions were removed after each contactperiod for gamma spectrometric assay. The 129 keV gamma-ray peak ofPu²³⁹ was measured in all aqueous portions, both before and aftercontact with the resin. The difference between these two measurementsrepresented the quantity of Pu(IV) sorbed onto the resin. The results ofthis testing are set forth in Tables 1 and 2, which set forth the Kdvalues (mL/g, Table 1; mL/meq alkyl, Table 2) for the various resins atthe given contact times and HNO₃ concentrations. These results show thesuperior affinity for Pu(IV) possessed by the resins of the invention,which have relatively longer-chain alkyl groups (C₄ -C₈) as compared tothe REILLEX™ 425 HPQ material. In addition, the inventive resinsdemonstrated good sorption kinetics for Pu(IV), leading to advantageous,relatively rapid loading of the resins.

                                      TABLE 1                                     __________________________________________________________________________         Contact                                                                             Reillex ™ HPQ                                                                       Ex. 1                                                                            Ex. 2                                                                             Ex. 3                                                                            Ex. 4                                                                            Ex. 5                                        [HNO.sub.3 ]                                                                       Time (hr)                                                                           methyl   butyl                                                                            hexyl                                                                             octyl                                                                            butyl                                                                            i-butyl                                      __________________________________________________________________________    1 M  0.5   6.7      17 23  22 20 9.6                                               2     7.1      19 26  16 21 10                                                6     6.8      19 27  19 22 11                                           3 M  0.5   69       108                                                                              104 42 122                                                                              65                                                2     97       193                                                                              250 131                                                                              240                                                                              105                                               6     100      209                                                                              306 200                                                                              285                                                                              117                                          5 M  0.5   233      232                                                                              165 85 254                                                                              188                                               2     412      561                                                                              703 303                                                                              868                                                                              440                                               6     372      677                                                                              1184                                                                              855                                                                              915                                                                              435                                          7 M  0.5   490      328                                                                              281 164                                                                              453                                                                              262                                               2     850      878                                                                              1339                                                                              960                                                                              1378                                                                             763                                               6     683      1488                                                                             2349                                                                              2251                                                                             1578                                                                             888                                          9 M  0.5   378      343                                                                              337 258                                                                              497                                                                              284                                               2     1164     1088                                                                             1177                                                                              974                                                                              1616                                                                             919                                               6     1517     1503                                                                             2026                                                                              1683                                                                             2243                                                                             1255                                         __________________________________________________________________________

                                      TABLE 2                                     __________________________________________________________________________         Contact                                                                             Reillex ™ HPQ                                                                       Ex. 1                                                                            Ex. 2                                                                             Ex. 3                                                                             Ex. 4                                                                            Ex. 5                                       [HNO.sub.3 ]                                                                       Time (hr)                                                                           methyl   butyl                                                                            hexyl                                                                             octyl                                                                             butyl                                                                            i-butyl                                     __________________________________________________________________________    1 M  0.5   2.2      8.4                                                                              11.6                                                                              4.9 5.6                                                                              4.4                                              2     2.3      9.4                                                                              13  7.1 5.9                                                                              4.6                                              6     2.2      9.4                                                                              14  8.5 6.2                                                                              5.0                                         3 M  0.5   23       53 53  19  34 30                                               2     32       95 126 58  67 48                                               6     33       103                                                                              155 89  80 53                                          5 M  0.5   77       114                                                                              83  38  71 85                                               2     136      276                                                                              355 135 244                                                                              200                                              6     123      334                                                                              598 382 257                                                                              198                                         7 M  0.5   162      162                                                                              142 73  127                                                                              119                                              2     281      433                                                                              676 429 387                                                                              347                                              6     225      733                                                                              1186                                                                              1005                                                                              443                                                                              404                                         9 M  0.5   125      169                                                                              170 115 140                                                                              129                                              2     384      536                                                                              594 435 454                                                                              418                                              6     501      740                                                                              1023                                                                              751 630                                                                              570                                         __________________________________________________________________________

EXAMPLE 7 Analysis of Resins for Affinity for Pertechnetate Ions

The inventive resins of Examples 1-5 were assayed for affinity forpertechnetate ions as compared to the REILLEX™ HPQ resin, using dynamiccontact procedures generally corresponding to those in Example 6. Thetest solutions were alkaline simulant solutions for Hanford Waste Tank101-SY (containing EDTA) in Richland, Wash. The results, set forth inTable 3 (Kd, mL/meq alkyl), demonstrate the unexpectedly superioraffinity of the inventive resins for pertechnetate ions.

                  TABLE 3                                                         ______________________________________                                        Contact Reillex ™ Ex. 1    Ex. 2   Ex. 3                                   Time (hr)                                                                             HPQ (methyl) (n-butyl)                                                                              (n-hexyl)                                                                             (n-octyl)                               ______________________________________                                        0.5     153          336      304     112                                     2       214          595      588     237                                     6       221          693      710     348                                     ______________________________________                                    

EXAMPLE 8

The procedure of Example 7 was repeated, except using a generic HanfordWaste Complexant Concentrate Simulant instead of one specific to TankSY-101. The results, set forth in Table 4 (Kd, mL/meq alkyl), againdemonstrate the superior affinity and sorption kinetics of the inventiveresins as regards the pertechnetate ion.

                  TABLE 4                                                         ______________________________________                                        Contact Reillex ™ Ex. 1    Ex. 2   Ex. 5                                   Time (hr)                                                                             HPQ (methyl) (n-butyl)                                                                              (n-hexyl)                                                                             (isobutyl)                              ______________________________________                                        0.5     123          312      288     219                                     2       164          496      486     331                                     6       162          504      551     368                                     ______________________________________                                    

While the invention has been described in some detail in the foregoingpassages, it will be understood that all additions and modificationswithin the spirit and scope of the invention are desired to beprotected. In addition, all publications cited herein are herebyincorporated by reference as if each had been individually incorporatedby reference and fully set forth.

What is claimed is:
 1. An anion-exchange resin exhibiting high affinityfor anions of technetium and plutonium, said resin comprising:abead-form macroreticular polyvinylpyridine resin crosslinked at leastabout 15% with divinylbenzene, said resin having pendant pyridinylgroups of which at least 20% are 1-alkyl-pyridinium groups, whereinalkyl groups of said 1-alkyl-pyridinyl groups have from 4 to 8 carbonatoms.
 2. The resin of claim 1, wherein said alkyl groups have 4 to 6carbon atoms.
 3. The resin of claim 2, wherein said alkyl groups aren-butyl, isobutyl, n-pentyl or n-hexyl.
 4. The resin of claim 3,wherein, said alkyl groups are n-butyl.
 5. The resin of claim 3, whereinsaid alkyl groups are isobutyl.
 6. The resin of claim 3, wherein saidalkyl groups are n-hexyl.
 7. A strong base anion-exchange resinexhibiting high affinity for anions of technetium and plutonium,comprising:a bead form polyvinylpyridine resin crosslinked with 15% to50% divinylbenzene, said resin bearing pendant pyridinyl groups at leastabout 20% of which have been alkylated with a branched or unbranchedalkyl halide having 4 to 8 carbon atoms.
 8. The resin of claim 7, whichis a macroreticular or gel form resin.
 9. The resin of claim 8, in whichsaid pendant pyridinyl groups are 2-pyridinyl groups or 4-pyridinylgroups.
 10. The resin of claim 9, in which said pendant pyridinyl groupsare 4-pyridinyl groups.
 11. The resin of claim 10, wherein said alkylhalide has 4 to 6 carbon atoms.
 12. The resin of claim 11, wherein saidalkyl halide is an alkyl chloride or alkyl bromide.
 13. The resin ofclaim 12, wherein said alkyl halide is an alkyl chloride.
 14. The resinof claim 13, wherein said alkyl halide is n-butyl chloride or n-hexylchloride.
 15. An anion-exchange resin material exhibiting high affinityfor anions of technetium and plutonium, comprising:a 15% to 50%divinylbenzene-crosslinked, quaternized polyvinylpyridine resin, saidresin having repeating units bearing pendant pyridinyl groups, whereinat least 20% of said repeating units are of the formula (I): ##STR3##wherein R is a branched or unbranched alkyl group having 4 to 8 carbonatoms.
 16. An anion-exchange material having high affinity for plutoniumand technetium anions, comprising:a divinylbenzene-crosslinkedvinylpyridine copolymer, said copolymer being comprised about 50% to 85%by weight of pyridinyl repeating units, a portion of said pyridinylrepeating units having the formula (I): ##STR4## wherein R is a branchedor unbranched alkyl group having 4 to 8 carbon atoms and X is an anion,and the remainder of said pyridinyl repeating units having the formula(II): ##STR5## or an acid salt form thereof, and wherein the mole ratioof groups (I) to (II) is at least about 1:4.
 17. An anion-exchange resinhaving high affinity for anions of technetium and plutonium,comprising:a bead form, macroreticular resin formed from a copolymer ofvinylpyridine and divinylbenzene, said resin having random crosslinkingunits, and functional repeating units consisting essentially of 20 mole% to 95 mole % pyridinium units of the formula (I): ##STR6## and 80% to5% pyridinyl units of the formula (II): ##STR7## and/or acid salt formsthereof.
 18. An anion-exchange resin having high affinity for anions oftechnetium and plutonium, comprising:a bead-form, macroreticular resincrosslinked with at least about 15% by weight divinylbenzene, said resinbeing comprised at least about 20% by weight of repeating units of theformula (I): ##STR8## wherein R is a branched or unbranched alkyl grouphaving 4 to 8 carbon atoms, and X⁻ is an anion.